Spreader stoker furnaces



May 24, 1955 '.1. D. KUPPENHEIMER SPREADER sToKER FURNAcEs Filed June 14, 1951 INVENTOR B'Y @awr f @-zv ATTORNEY May 24, 1955 J. D. KUPPENHElMl-:R

SPREADER sToKER FURNACES 2 Sheets-Sheet 2 Filed June 14, 1951 INVENTOR Jo/nv KuPPENHE/MER BY @auf f r ATTORNEY United States Patent O 2,708,890 SPREADER STGKER FURNACES John D. Kuppenheimer, Worcester, Mass., assignor to Riley Stoker Corporation, Worcester, Mass., a corporation of Massachusetts Application June 14, 1951, Serial No. 231,631 2 Claims. (Cl. 110-40) This invention relates to spreader stoker furnaces, and more particularly to furnaces of this type adapted for use in connection with steam generators of large capacity.

The usual spreader stoker comprises a fuel projecting means, for example a rotatable device in the nature of a paddle wheel, located adjacent an opening in a furnace wall. Fuel, such as crushed coal, is supplied to this wheel from a hopper at a desired rate by a reciprocable ram or other suitable means. The rotating wheel throws the fuel through the opening into the furnace and on to a grate, which is preferably of the endless traveling type. In large furnaces, several stokers are usually arranged in a row along one of the furnace walls, all supplyingrfuel to the same grate.

High capacity steam generators require large furnaces, with grates of considerable area, in order that sufficient fuel may be burned to produce steam at the required rate. It is found however that if a spreader stoker is employed to throw fuel over too great a distance, the fuel will not be distributed as evenly as is required for the best results. At the present time twenty feet appears to be about the maximum practical throw for such a stoker. This fact has limited the size of spreader stoker furnaces. Large steam generators usually include superheaters having a series of elements distributed across the width of the furnace. In order to avoid overheating of any of these superheater elements, it is very-important that the temperature of the hot gases flowing over them be substantially uniform across the furnace. This has presented a serious problem in prior installations. `Most of the large modern steam generators include horizontal drums which extend transversely of the furnace. Such drums are very expensive, and in order to minimize the cost of the installation it is considered wise to make the furnace width as small as possible, since this width determines the length of the drums.l However, for a given required grate area, a reduction in the furnace width necessitates an increase in the length of the furnace, from front to rear. Inasmuch as most spreader stoker furnaces have heretofore been tired through the front wall, a long furnace complicates the problem of fuel distribution.

It is accordingly one object of the invention to provide a spreader Stoker furnace of large grate area, with the construction and arrangement such that good distribution of fuel may be obtained over such area.

It is a further object of the invention to provide a spreader stoker furnace in association with a steam gen erator and superheater, the parts being so constructed and arranged that hot gases reaching the superheater will be of uniform temperature across the width thereof.

It is a further object of the invention to provide a spreader stoker furnace of large capacity for use in connection with a steam generator having transverse drums, the furnace being comparatively long, from front to rear, and the construction being such as to ensure good fuel distribution over the entire grate surface.

With these and other objects in view,

as will be apparent to those skilled in the art, the invention resides in the comcal bination of parts set forth in the specification and covered by the claims appended hereto.

In accordance with the invention in its preferred form there is provided a furnace having two upright side walls and two upright end walls enclosing a furnace chamber of rectangular shape, the distance between the end walls preferably exceeding that between the side walls. Within the furnace there is mounted an endless traveling grate with its upper run arranged to travel horizontally from one side wall toward the other. Each side wall is provided with a plurality of openings, located above the grate, and adjacent each opening there is mounted a spreader stoker to throw fuel through the opening and on to the grate. With stokers on each side wall, the stokers are required to distribute the fuel throughout only half the length of the grate. Preferably two endless grates are provided, in a side by side arrangement, with their upper runs traveling in opposed directions. This makes possible a substantially uniform distribution of the hot gases across the furnace, which is very important when the furnace is associated with a steam generator and superheater.

Referring to the drawings illustrating one embodiment of the invention, and in which like reference numerals indicate like parts,

Fig. l is a vertical longitudinal section through av spreader stoker furnace and an associated steam generator, taken on the line 1-1 of Fig. 2;

Fig. 2 is a section taken on the line 2 2 of Fig. l;

Fig. 3 is a section taken on the line 3 3 of Fig. l; and

Fig. 4 is a section taken on the line 4-4 of Fig. 1.

The embodiment illustrated comprises a furnace or combustion chamber 1t) of generally rectangular shape in plan. This furnace includes a front wall 11, a rear Wall 12, and two side walls 14 and l5. The width of the furnace is somewhat less than its length. Thus the side walls 14 and 15 may be say twenty-four feet apart, with the walls 11 and 12 say thirty feet apart.

The furnace 10 provides hot gases for the operation of a large water-tube steam generator 17 of well-known construction. This steam generator includes a transverse horizontal water drum 18 located near the top of the furnace rear wall 12, a transverse horizontal steam-andwater drum 19 spaced above the drum 18, and a transverse horizontal header 20 located near the top of the furnace front wall 11. A bank of upright water tubes 22 connect the drums 18 and 19. Two rows of water tubes 23 connect the drum 18 to the header 20, and two rows of water tubes 24 connect the header 20 to the steam-and-water drum 19. A superheater 26 is located in the space between the tubes 23 and 24. This superheater is of a wellknown type having a plurality of laterally adjacent multiple-loop tubular elements distributed across the path of the gases leaving the combustion chamber, with the opposite ends of the said elements connected respectively to an inlet header 27 and to an outlet header 28. The inlet header 27 is connected to the steam space of the upper drum 19 by tubes 29. A gas outlet duct 31 with a damper 32 therein is located near the upper drum 19. Bales 34 and 3S cause the gases from the furnace 10 to flow into contact with the superheater 26 and then into contact with the water tubes 22 before escaping through the duct 31.

ln order to support a fuel bed for combustion purposes, there are provided two endless traveling grates 37 and 38 in the lower portion of the furnace 10. The grate 37 is located in front of the grate 38, the two grates being positioned side by side with their upper surfaces in a common horizontal plane. The upper run of the grate 37 is arranged to travel toward an ash pit 40 beneath the furnace side wall 14, whereas the upper run of the grate 38 is arranged to travel in the opposite direction toward an ash pit 41 beneath the furnace side wall 15. The spaces beneath the upper runs of the grates are divided in known manner by frame members or partitions 43 into separate compartments 44 which extend transversely with respect to the directions of grate travel. These compartments are supplied with independently controlled supplies of air by means of branch ducts 46 leading from main air ducts 47, each branch duct having a damper` 45 therein. Each furnace side wall 14 and 15 has a horizontal row of spaced openings 50 therein, somewhat above the tops of the grates 37 and 38. A spreader stoker or feeder 52 is mounted adjacent the outer end of each opening 50 in position to project fuel therethrough into the furnace. The stokers 52 may be of any suitable and well-known construction adapted to distribute the fuel uniformly over the adjacent portions of the grate surface, one such stoker being disclosed in the United States patent to Miller No. 2.538,944, granted January 23, 1951.

The operation of the invention will now be apparent from the above disclosure. The stokers 52 will supply fuel to the grates 37 and 33, and since each stoker has to project fuel only one-half the width of the furnace, it is possible to obtain excellent distribution of the fuel even though the furnace be an extremely large one. Thus, if the width of the furnace is twenty-four feet, each stoker need distribute fuel over only twelve feet of grate surface. The grates 37 and 3S will travel slowly toward the ash pits 40 and 41 respectively, and as combustion of the fuel takes place there will be a deposit of ash on the grate surface. The depth of this ash deposit will increase in the direction of grate travel, and as the moving grates reach their respective ash pits the ash will be discharged into the pits by gravity. Because of the increasing thickness of the ash layer on the grates, the resistance to the flow of air upwardly through the fuel bed will also increase. While the dampers 48 can be adjusted to compensate for this increasing resistance to some extent, it is nevertheless a fact that the temperature and probably other properties of the hot gases above each grate will vary from one end of the grate to the other. However the two grates travel in opposite directions, and as a result the properties of the gases will become very uniform as they rise and mingle in the furnace chamber 1t), and particularly as they travel upwardly across the water tubes 23 in front of the baffle 34 and come into contact with the superheater 26. Consequently, all elements of the superheater will be subjected to the heating effort of gases at substantially the same temperature. This is extremely important and desirable, particularly since it avoids the danger of overheating one or more of the superheater elements. It will be noted that in the very large furnace described, with a distance of thirty feet between the front wall 11 and the rear wall 12, each grate need be only fifteen feet wide.

The invention is well adapted for use with high capacity water tube steam generators with transverse drums, since for several reasons a long and relatively narrow furnace is desirable for such steam generators.

Having thus described my invention, what I claim as new and desire to secure by Letters Patent is:

1. A spreader stoker furnace comprising forward, rearward and side walls defining a combustion chamber, a gas exit opening at the upper portion of the combustion charnber, separate ash pits adjacent the respective side walls, at least two endless traveling grates in the lower portion of the chamber in positions laterally adjacent to one another and each having an upper run extending completely from one side wall to the other, one of said upper runs being arranged to travel toward one of said side walls and to deposit ash in the adjacent ash pit, an immediate adjacent upper run being arranged to travel toward the other of said side walls and to deposit ash in the adjacent ash pit, each of said side walls having openings therethrough spaced above each upper run at both ends thereof, a spreader Stoker mounted adjacent each opening and arranged to project fuel therethrough into the combustion chamber for deposit on the adjacent upper run, and a sepalately-controlled source of air connected to the zone under cach of the upper runs.

2. A furnace comprising a combustion chamber having two opposed upright side walls, two endless traveling grates in the lower portion of the chamber in positions laterally adjacent to one another and each having an upper run extending continuously from side wall to side wall, one of said upper runs being arranged to travel toward one of said side walls and the other run being arranged to travel in the opposite direction, each of said walls having openings therethrough spaced above each grate at both ends thereof, and a spreader stoker mounted adjacent each opening and arranged to project fuel therethrough into the combustion chamber for deposit on the adjacent grate over an area extending approximately one-half the distance to the opposite wall.

References Cited in the le of this patent UNITED STATES PATENTS (Corresponding U. S. 2,567,837, Sept. 1l, 1951) 

